A gear part of the present invention includes a lubrication coating formed
on a surface of the gear part, the lubrication coating containing an
organic phosphorous compound. In the gear part, when a tooth surface of
the gear part is engaged with a tooth surface of a counter member, the
organic phosphorous compound is transferred to the tooth surface of the
counter member and another lubrication coating containing the organic
phosphorous compound is formed on the tooth surface of the counter
member. As a result, the lubrication coating can be held on the surface
of the gear part for long periods.